Acquired cardiovascular disease
The effect of surgeon volume on mortality for off-pump coronary artery bypass grafting

Read at the 91st Annual Meeting of The American Association for Thoracic Surgery, Philadelphia, Pennsylvania, May 7-11, 2011.
https://doi.org/10.1016/j.jtcvs.2011.12.048Get rights and content
Under an Elsevier user license
open archive

Objective

Recent trials comparing on-pump (CABG) with off-pump coronary artery bypass grafting (OPCAB) have been criticized by those who believe that surgeon inexperience may explain the apparent worse outcomes for OPCAB. However, the true effect of surgeon volume on outcomes after OPCAB remains unknown. The purpose of this study was to examine the effect of surgeon volume on risk-adjusted mortality after OPCAB.

Methods

From 2003 to 2007, 709,483 patients underwent coronary artery bypass grafting operations (CABG = 439,253; OPCAB = 270,230) within the Nationwide Inpatient Sample database. Hierarchic generalized linear regression modeling with spline functions for annual individual operating surgeon volume was used to assess the relationship between annual surgeon volume and inpatient mortality, adjusted for comorbid disease and other potential confounders.

Results

OPCAB was performed in 38.1% of coronary artery bypass grafting operations. The average age for those undergoing OPCAB was 66.1 ± 11.1 years, and female patients accounted for 29.3% of operations with 1-vessel (20.4%), 2-vessel (36.6%), 3-vessel (20.5%), or 4 vessels or more (13.6%). Median surgeon volume for OPCAB was 105 (56–156) operations per year. A highly significant nonlinear relationship between surgeon volume and risk-adjusted mortality was observed for OPCAB operations (P < .01). Specifically, an estimated 5% decrease in the absolute probability of death occurred after OPCAB performed by the surgeons with the highest volume, which is greater than the 3% estimated decrease for conventional CABG. Of note, the effect of surgeon volume on mortality was significantly less than other risk factors, such as the presence of heart failure, renal failure, type of bypass conduit, and gender.

Conclusions

A significant surgeon volume–outcome relationship exists for mortality after OPCAB with a threshold of more than 50 operations per year. However, the contribution of surgeon volume to the probability of death is incrementally small compared with other patient and operative characteristics. This demonstrates that outcomes after OPCAB are more dependent on patient risk factors than on surgeon volume.

CTSNet classification

23.1
23.1.4

Abbreviations and Acronyms

CABG
coronary artery bypass grafting
CPB
cardiopulmonary bypass
ICD-9-CM
International Classification of Diseases-Ninth Revision, Clinical Modification
ITA
internal thoracic artery
NIS
Nationwide Inpatient Sample
OPCAB
off-pump coronary artery bypass

Cited by (0)

This study was supported by Award Number 2T32HL007849-11A1 (to I.L.K.) from the National Heart, Lung, and Blood Institute and the Thoracic Surgery Foundation for Research and Education Research Grant (to G.A.). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Heart, Lung, and Blood Institute or the National Institutes of Health.

Disclosures: Authors have nothing to disclose with regard to commercial support.